I need help of shift mcu

[DRCRecoveryData]

Hi,

I have built a tool to repair encrypted JPEG files affected by stop/djvu ransomware. It encrypts 153605 bytes from the header. However, when I shift the MCU to fix alignment, the left column appears distorted and glitches up by one MCU in the column.

After moving the good header to the encrypted JPEG header...

The bottom has both good and non-MCU sections

After counting the number of non-MCU units from those bottom scanlines to shift the MCU, upon shifting to correct alignment, the left column becomes distorted and glitches up by one MCU in the column.

Can you help me to fix my code?

import sys
import os
import re
import numpy as np
from PyQt6.QtWidgets import QApplication, QWidget, QVBoxLayout, QPushButton, QFileDialog, QTextEdit, QLabel, QLineEdit
from PyQt6.QtCore import Qt
from PIL import Image, ImageOps, ImageEnhance

class JpegToolGUI(QWidget):
    def __init__(self):
        super().__init__()
        self.initUI()

    def initUI(self):
        self.setWindowTitle("JPEG Repair Tool")
        self.setGeometry(100, 100, 400, 400)

        self.setStyleSheet('''
            QPushButton {
                background-color: #007ACC;
                color: white;
                border: none;
                border-radius: 5px;
                padding: 8px 16px;
            }

            QPushButton:hover {
                background-color: #005F99;
            }

            QTextEdit {
                background-color: #D9E6F5;
                color: black;
                border-radius: 5px;
                padding: 8px;
            }
        ''')

        self.layout = QVBoxLayout()

        # Create buttons
        self.btnSelectReference = QPushButton("Select Reference JPEG")
        self.btnSelectEncryptedFolder = QPushButton("Select Encrypted Folder")
        self.btnRepairJpeg = QPushButton("Repair JPEGs")
        self.btnShiftMcu = QPushButton("Shift MCU")
        self.btnAutoColor = QPushButton("Auto Color")

        # Create text output area
        self.outputText = QTextEdit()
        self.outputText.setReadOnly(True)

        # Create input fields
        self.reference_jpeg_input = QLineEdit()
        self.encrypted_folder_input = QLineEdit()

        # Add widgets to layout
        self.layout.addWidget(QLabel("Reference JPEG:"))
        self.layout.addWidget(self.reference_jpeg_input)
        self.layout.addWidget(self.btnSelectReference)
        self.layout.addWidget(QLabel("Encrypted Folder:"))
        self.layout.addWidget(self.encrypted_folder_input)
        self.layout.addWidget(self.btnSelectEncryptedFolder)
        self.layout.addWidget(self.btnRepairJpeg)
        self.layout.addWidget(self.btnShiftMcu)
        self.layout.addWidget(self.btnAutoColor)
        self.layout.addWidget(self.outputText)

        self.setLayout(self.layout)

        # Connect button actions
        self.btnSelectReference.clicked.connect(self.selectReferenceJPEG)
        self.btnSelectEncryptedFolder.clicked.connect(self.selectEncryptedFolder)
        self.btnRepairJpeg.clicked.connect(self.repairJPEGs)
        self.btnShiftMcu.clicked.connect(self.shift_mcu)
        self.btnAutoColor.clicked.connect(self.autoColorImages)

    def selectReferenceJPEG(self):
        fileName, _ = QFileDialog.getOpenFileName(self, "Select Reference JPEG", "", "JPEG Files (*.jpg);;All Files (*)")

        if fileName:
            self.reference_jpeg_input.setText(fileName)

    def selectEncryptedFolder(self):
        folderName = QFileDialog.getExistingDirectory(self, "Select Encrypted Folder")

        if folderName:
            self.encrypted_folder_input.setText(folderName)

    def repairJPEGs(self):
        reference_jpeg = self.reference_jpeg_input.text().strip()
        encrypted_folder = self.encrypted_folder_input.text().strip()

        if not os.path.exists(reference_jpeg) or not os.path.exists(encrypted_folder):
            self.outputText.append("Please select the reference JPEG and encrypted folder.")
            return

        repaired_folder = os.path.join(encrypted_folder, "Repaired")
        if not os.path.exists(repaired_folder):
            os.makedirs(repaired_folder)

        pattern = re.compile(r".*\.JPG\..{4}$", re.I)

        for encrypted_file in os.listdir(encrypted_folder):
            if pattern.match(encrypted_file):  # Matches files like *.JPG.****
                output_file = os.path.join(repaired_folder, os.path.splitext(encrypted_file)[0].rsplit('.', 1)[0] + '.JPG')
                offset = self.find_jpeg_markers(reference_jpeg, 'ECS')
                self.dd_replacement(reference_jpeg, output_file, bs=1, count=offset)
                self.dd_replacement(os.path.join(encrypted_folder, encrypted_file), output_file, bs=1024, skip=153605)
                self.outputText.append(f"Processed {encrypted_file} to {output_file}")

        self.outputText.append("Repair complete.")

    def find_jpeg_markers(self, filename, marker=None):
        with open(filename, "rb") as f:
            s = f.read()

        marker_name = {
            0xd8: "SOI", 0xe0: "APP0", 0xe1: "APP1", 0xdb: "DQT",
            0xc0: "SOF", 0xc4: "DHT", 0xda: "SOS", 0xd9: "EOI",
            0: "ECS"
        }

        segments = {}
        offset = 0

        while True:
            f = s.find(b"\xff", offset)
            if f < 0:
                break

            offset = f + 2
            if offset <= len(s):
                m = s[f + 1]
                if m in marker_name:
                    segments[f] = m

        if marker and marker.upper() == "ECS":
            last_sos_offset = None
            for f in reversed(sorted(segments.keys())):
                if marker_name[segments[f]] == "SOS":
                    last_sos_offset = f
                    break

            if last_sos_offset is not None:
                return last_sos_offset + 12
        elif marker:
            for f in reversed(sorted(segments.keys())):
                if marker_name[segments[f]] == marker.upper():
                    return f
        else:
            offsets = [(marker_name[segments[f]], f) for f in sorted(segments.keys())]
            return offsets

    def dd_replacement(self, input_file, output_file, bs=1, count=None, skip=None):
        with open(input_file, "rb") as f:
            if skip:
                f.seek(skip)

            data = f.read(bs * count if count else -1)

        with open(output_file, "ab") as f:
            f.write(data)

    def autoColorImages(self):
        repaired_folder = os.path.join(self.encrypted_folder_input.text().strip(), "Repaired")
        if not os.path.exists(repaired_folder):
            self.outputText.append("Repaired folder not found.")
            return

        jpg_files = [f for f in os.listdir(repaired_folder) if f.lower().endswith(".jpg")]

        if not jpg_files:
            self.outputText.append("No JPG files found in the Repaired folder.")
            return

        for jpg_file in jpg_files:
            image_path = os.path.join(repaired_folder, jpg_file)
            try:
                im = Image.open(image_path)
                im = ImageOps.autocontrast(im, cutoff=1)
                enhancer = ImageEnhance.Sharpness(im).enhance(3)
                im = ImageOps.posterize(im, bits=8)
                enhancer = ImageEnhance.Color(im).enhance(3)
                im.save(image_path, quality="maximum")
                self.outputText.append(f"Auto color applied to {jpg_file} and saved.")
            except Exception as e:
                self.outputText.append(f"Error processing image {jpg_file}: {str(e)}")

        self.outputText.append("Auto Color process complete.")

    def shift_mcu(self):
        reference_jpeg = self.reference_jpeg_input.text().strip()
        encrypted_folder = self.encrypted_folder_input.text().strip()

        if not os.path.exists(reference_jpeg) or not os.path.exists(encrypted_folder):
            self.outputText.append("Please select the reference JPEG and encrypted folder.")
            return

        repaired_folder = os.path.join(encrypted_folder, "Repaired")
        if not os.path.exists(repaired_folder):
            self.outputText.append("Repaired folder not found. Run Repair JPEGs first.")
            return

        jpg_files = [f for f in os.listdir(repaired_folder) if f.lower().endswith(".jpg")]

        if not jpg_files:
            self.outputText.append("No JPG files found in the Repaired folder.")
            return

        for jpg_file in jpg_files:
            image_path = os.path.join(repaired_folder, jpg_file)
            try:
                img = Image.open(image_path)
                data = np.array(img, dtype=np.uint8)
            except Exception as e:
                self.outputText.append(f"Error opening image {jpg_file}: {str(e)}")
                continue

            num_good_mcu = self.auto_detect_shift(data)
            if num_good_mcu == 0:
                self.outputText.append(f"No MCU shift needed for {jpg_file}.")
                continue

            width_to_shift = num_good_mcu * 8
            shifted_data = np.hstack((data[:, width_to_shift:], data[:, :width_to_shift]))

            height, width, _ = shifted_data.shape
            while height >= 8 and np.array_equal(shifted_data[height - 8:height, :, :], np.ones((8, width, 3), dtype=np.uint8) * 128):
                height -= 8

            height -= 8
            width -= 16

            cropped_data = shifted_data[:height, :width, :]

            output_img = Image.fromarray(cropped_data)
            output_img.save(image_path, "JPEG")

            self.outputText.append(f"Shifted and saved image {jpg_file} to: {image_path}")

        self.outputText.append("MCU Shift process complete.")

    def auto_detect_shift(self, data):
        block_size = 8
        height, width, _ = data.shape

        while height >= block_size:
            if np.array_equal(data[height - block_size:height, :, :], np.ones((block_size, width, 3), dtype=np.uint8) * 128):
                height -= block_size
            else:
                break
        cropped_data = data[:height, :, :]

        for j in range(0, width, block_size):
            mcu = cropped_data[height - block_size:height, j:j + block_size, :]
            gray_mcu = np.ones((block_size, block_size, 3), dtype=np.uint8) * 128

            diff = np.abs(mcu.astype(int) - gray_mcu.astype(int))
            avg_diff = np.mean(diff)

            if avg_diff < 10:
                return j // block_size

        return width // block_size

def main():
    app = QApplication(sys.argv)
    window = JpegToolGUI()
    window.show()
    sys.exit(app.exec())

if __name__ == "__main__":
    main()

Sample files:
Pictures.zip

[albmac]

I would say that you are simply losing the first N MCUs in the stream, so everything is shifted.
Probably the header you copy points to the wrong starting point in the file.

[DRCRecoveryData]

I would say that you are simply losing the first N MCUs in the stream, so everything is shifted. Probably the header you copy points to the wrong starting point in the file.

Can you check the code to correct it?

[albmac]

Sorry but I can't